<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .c1{
            height: 100px;
            width: 100px;
            background-color: red;

        }

    </style>
</head>
<body>

<div class="c1"></div>


</body>
<script src="jquery.js"></script>
<script>

    $('.c1').data('username','xiaolong');


    function f() {
        $('.c1').data('username');
    }

</script>

</html>